Ferro-alloys containing niobium and titanium



United States Patent Int. (:1. C22c 39/04, 39/54 US. Cl. 75-124 3 Claims ABSTRACT OF THE DISCLOSURE The loss by oxidation of niobium and titanium in ferroalloys containing such alloying elements simply, when used in steel-making, is inhibited if a ferro-alloy is used containing both titanium and niobium, together with a small proportion of aluminium, silicon and carbon.

This invention relates to a ferro-alloy containing niobium and titanium.

It is known that structural steels, such as are used for example in fabricating large diameter tubes, may have a low carbon content of about 0.2% so that the steels are weldable. In such steels about 0.02% of niobium is added to make good the consequent reduction in tensile and yield strength, and the incorporation of about 0.07% titanium has also proved to be useful for grain refinement.

Such steels are cast semi-killed or completely deoxidised with aluminium, and the alloying elements niobium and titanium are added in the ladle. For this purpose ferroalloys are used, namely a ferro-titanium containing 30 to 40% titanium, and a ferro-niobium containing 60% niobium and 2 to 6% tantalum, as well as certain quantities of silicon and aluminium. This conventional procedure results in a considerable loss by oxidation of the alloying components, and the distribution of the alloying elements in the final steel is not always uniform, as is desirable, and the steel may contain occlusions.

It has been discovered that the manner in which the alloying elements are added has a considerable effect on the uniformity of their distribution in the steel and upon oxidation loss, and the invention provides a ferro-alloy which is capable of ensuring a uniform distribution of the alloying elements in the steel and reducing oxidation loss to a surprising extent, and which without precautions is capable of dissolution in the ladle by virtue of the heat content thereof.

The invention comprises a ferro-alloy consisting essentially of 25 to 50% titanium, to 25% niobium, 1 to 10% aluminium, 1 to 5% silicon and 0 to 0.5% carbon, the remainder being iron. By the term consisting essentially of used herein and in the claims is meant that impurities and such incidental ingredients which do not significantly affect the stated characteristics of the alloy, may be present in small proportions.

In the ferro-alloy according to the invention, the titanium-niobium ratio is preferably between 5 :1 and 1:1,

The oxidation loss occasioned by the use of the ferro- 3,442,644 Patented May 6, 1969 alloys of the invention is less and the titanium and niobium yield is therefore greater than when using ferroalloys which contain either only titanium or only niobium. The melting range of the ferro-alloys of the invention is lower than that of conventional ferro-niobium, being from to C. lower.

An alloy which is particularly effective for the stated purpose, consists essentially of 35 to 40% titanium, 12 to 15% niobium, 5 to 10% aluminium, 2 to 5% silicon and about 0.1% carbon, the remainder being iron.

The melting range of the said preferred ferro-alloy is between 1430 and 1450 C. By the use of the said alloy in the production of a steel to contain 0.2% carbon, 0.015% sulphur, 0.025% phosphorous, 1.05% manganese, 0.025% niobium, 0.07% titanium, remainder iron, a titanium yield of 83% and a niobium yield of 78% of the required amount were achieved, Whereas a titanium yield of only 47% and a niobium yield of only 61% were achieved when adding ferro-titanium and ferro-niobium individually. Further the solubility of the ferro-alloy according to the invention was very much better than that of the ferro-alloys separately introduced. Consequently the alloying process in the ladle was completed in the ladle within a shorter length of time than that needed in the case of the conventional alloys. This useful result is assisted by the fact that the melting range of the ferro-alloy is relatively low. Moreover, the resultant steel has fewer occlusions.

The introduction of a ferro-alloy according to the invention in the production of the specified steels therefore results in a simpler, more economic and more readily controllable process, leading to a high utilisation of the resultant casting in further processing. A concomitant factor which likewise favourably affects the economy of the process is that the quantity of the addition may be reduced, because of the higher yields that are obtained.

What is calimed is:

1. A ferro-alloy consisting essentially of 25 to 50%. titanium, 5 to 25% niobium, 1 to 10% aluminium, 1 to 5% silicon and 0 to 0.5% carbon, the remainder being iron.

2 A ferro-alloy according to claim 1, characterised in that the ratio of titanium to niobium therein is between 5:1 and 1:1.

3. A ferro-alloy according to claim 1, consisting essentially of 35 to 40% titanium, 12 to 15% niobium, 5 to 10% aluminium, 2 to 5% silicon, and about 0.1% carbon, the remainder being iron.

References Cited UNITED STATES PATENTS 2,269,407 l/ 1942 Critchett et a1. 75-58 2,339,357 1/1944 Schafer 75--123 2,822,268 2/1958 Hix 75123 3,215,526 11/1965 Stoyell et al. 75-123 CHARLES N. LOVELL, Primary Examiner.

US. Cl. X.R. 

